Technologies of expanding genetic information of DNA through production of novel artificial base pairs have two potential application fields with high versatility, and artificial base pairs have been actively developed. One of the application fields is use of an artificial base pair functioning in replication, transcription, or translation for producing DNA, RNA, or protein having a novel structural component. The other of the application fields is use of an artificial base pair incorporated in a double-stranded nucleic acid, DNA or RNA, to increase the number of types of probe sequences composed of nucleic acid fragments, which can be used in a multiplex real-time PCR or DNA computer and further can be used as a novel codon or anticodon for introducing an artificial amino acid into a protein through translation.
Though a large number of fluorescent nucleic acid base analogs have been reported, no nucleic acid base analog showing a high quenching effect by the analog itself has been reported. Conventionally, quenching molecules such as a dabsyl group have been linked to nucleic acid bases via linkers. In this case, bases forming a base pair are not in complete contact with a fluorescent molecule lying near the bases; therefore the quenching effect is weak. Accordingly, the detection thereof needs an apparatus. Thus, prior to the present invention, no method could simply and efficiently detect a base pair using a quenching effect of a base.